/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/
#ifndef itkLevelSetTestFunction_h
#define itkLevelSetTestFunction_h

#include "itkLightObject.h"
#include "itkImage.h"

namespace itk
{

/**
 * \class LevelSetTestFunction
 *
 * \brief A simple function to compare the numerical methods of the level set classes
 * to the analytical values.
 *
 * \f$ f(x,y) = \sqrt{ (x-5)(x-5) + (y-4)(y-4) } - 3 \f$
 */
template< typename TPixel >
class ITK_TEMPLATE_EXPORT LevelSetTestFunction: public LightObject
{
public:
  ITK_DISALLOW_COPY_AND_ASSIGN(LevelSetTestFunction);

  using Self = LevelSetTestFunction;
  using Superclass = LightObject;
  using Pointer = SmartPointer< Self >;
  using ConstPointer = SmartPointer< const Self >;

  itkTypeMacro( LevelSetTestFunction, LightObject );

  itkNewMacro( Self );

  static constexpr unsigned int Dimension = 2;

  using PixelType = TPixel;

  using ImageType = Image< PixelType, Dimension >;
  using IndexType = typename ImageType::IndexType;
  using PointType = typename ImageType::PointType;

  using OutputRealType = typename NumericTraits< PixelType >::RealType;
  using GradientType = CovariantVector< OutputRealType, Dimension >;
  using HessianType = Matrix< OutputRealType, Dimension >;

  OutputRealType Evaluate( const PointType & point ) const;

  GradientType   EvaluateGradient( const PointType & point ) const;

protected:
  LevelSetTestFunction() = default;
};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkLevelSetTestFunction.hxx"
#endif

#endif
